Long before there was a Boulder Canyon Act or a Hoover Dam, the Colorado River flowed uninterrupted along its 1,450-mile course from the Rocky Mountains to the Gulf of California. Winding through California's richly fertile Imperial Valley, the Colorado River was unpredictable—flooding in the spring, drying up in the summer. The destruction caused when the river flooded in the spring had devastated the farmlands near its banks. By the 1920s, the damage attracted so much attention that it had become necessary and politically expedient to try to control the path of the lower Colorado. The only way to harness this indispensable resource was to build a dam, which in turn would provide badly needed electricity to the western states.

The Boulder Canyon Project Act of 1928 authorized construction of a dam in Boulder, or Black, Canyon, construction of the All-American Canal to connect the Imperial and Coachella Valleys with the Colorado River, and divided the lower basin waters among the lower basin states. In addition, the act appropriated $165,000,000 for construction and stated the primary purposes of the project as flood control, improvement of navigation on the Colorado River, storage and delivery of water for reclamation and other beneficial uses, and generation of power. The Boulder Canyon Project Act became effective on June 25, 1929, following ratification of the Colorado River Compact by six of the seven states of the Colorado River Basin.

Before work could start on the project, the Colorado River had to be diverted. To accomplish this, four tunnels, each 50 feet in diameter (which today could accommodate a 747 without the wings), were drilled through the solid rock walls of Black Canyon. When the dam was finished, it stood over 700 feet high, was 1,244 feet across at the top, 660 feet thick at the base, 45 feet thick at the top, and weighed 6.6 million tons; had a power generating capacity of 2.8 million kilowatts; and could store up to 2 years’ average flow from the Colorado River in Lake Mead.

About 16,000 men and women worked on the project with approximately 3,500 people employed at any one time. It was dangerous work, and the official death toll was 96. Five thousand men and their families settled in the Nevada desert, most in Boulder City, an efficiently run, well-ordered company town built by the Federal Government. Others lived in dozens of tent cities and honky-tonk towns that sprang up on the road from the dam to the small town of Las Vegas. To a country struggling to come out of the Depression, the project was dramatic evidence of what American brains and manpower could accomplish, and it was a symbol of hope for the dispossessed. In 1935 the job was finished.

No other politician was more responsible for the successful completion of Boulder Dam than Herbert Hoover. Because of his long involvement in the project, from his days as Secretary of Commerce to his tenure as 31st President, the 80th Congress, in 1947, passed legislation officially designating the dam “Hoover Dam.” Hoover had called it "the greatest engineering work of its character ever attempted by the hand of man."

For more information, visit the Bureau of Reclamation's The Boulder Canyon Project.